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The tegument of Schistosoma mansoni plays an integral role in host–parasite interactions, particularly during the transition from the free-living cercariae to the intra-mammalian schistosomula stages. This developmental period is characterised by the transition from a trilaminate surface to a heptalaminate tegument that plays key roles in immune evasion, nutrition and excretion. Proteins exposed at the surface membranes of newly transformed schistosomula are therefore thought to be prime targets for the development of new vaccines and drugs for schistosomiasis. Using a combination of tegumental labelling and high-throughput quantitative proteomics, more than 450 proteins were identified on the apical membrane of S. mansoni schistosomula, of which 200 had significantly regulated expression profiles at different stages of schistosomula development in vitro, including glucose transporters, sterols, heat shock proteins, antioxidant enzymes and peptidases. Current vaccine antigens were identified on the apical membrane ( Sm -TSP-1, calpain) or sub-tegumental ( Sm -TSP-2, Sm 29) fractions of the schistosomula, displaying localisation patterns that, in some cases, differ from that in the adult stage fluke. This work provides the first known in-depth proteomic analysis of the surface-exposed proteins in the schistosomula tegument, and some of the proteins identified are clear targets for the generation of new vaccines and drugs against schistosomiasis. [ABSTRACT FROM AUTHOR]

Background: Control of human hookworm infection would be greatly aided by the development of an effective vaccine. We aimed to develop a live attenuated human hookworm vaccine.Methods: This was a two-part clinical trial done at Q-Pharm in Brisbane (QLD, Australia) using a live ultraviolet C (UVC)-attenuated Necator americanus larvae vaccine. Part one was an open-label, dose-finding study using 50 L3 larvae suspended in water to a volume of 200 μL, attenuated with UVC exposure of 700 μJ (L3-700) or 1000 μJ (L3-1000). Part two was a randomised, double-blind, placebo-controlled, challenge study, in which participants were randomly assigned 2:1 to the vaccine group or placebo group. Healthy hookworm-naive adults aged 18-65 years with body-mass index 18-35 kg/m2 received two doses of either placebo (Tabasco sauce) or vaccine (50 L3-700) on day 1 and day 42, followed by challenge with 30 unattenuated L3 larvae to both groups. All participants received a single oral dose of 400 mg albendazole 4 weeks after each inoculation and a 3-day course (400 mg orally daily) initiated on day 161 after the challenge phase, to eliminate any remaining infection. The primary outcome of part 1 was the level of larval attenuation the resulted in a grade 2 or 3 dermal adverse event. The primary outcome of part 2 was safety and tolerability, assessed by frequency and severity of adverse events in all randomly assigned participants. Prespecified exploratory outcomes in the challenge study were faecal N americanus DNA concentration, the number of N americanus larvae recovered per g of faeces cultured, hookworm antigen-specific serum IgG antibody responses, and hookworm antigen-specific peripheral blood cytokine responses. The trial is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617001007325).Findings: Between Sept 19, 2017, and Oct 24, 2018, seven participants were enrolled into three cohorts in part one (two participants in cohort 1, who received L3-700; two participants in cohort 2, who received L3-700; and three participants in cohort 3, who received L3-1000) and a further 15 were enrolled into part two. There were no serious adverse events in part one or part two. In part one, a greater number of skin penetration sites were observed after administration of L3-700 than L3-1000 (mean 15·75 [95% CI 11·18 to 20·32] with L3-700 vs 4·33 [-1·40 to 10·07] with L3-1000). Similarly, greater erythema (median 225 mm2 [IQR 150 to 325] vs 25 mm2 [12·5 to 80]) and a longer duration of the dermal reaction (median 8·0 days [IQR 3·5 to 11·5] vs 2·0 days [2·0 to 4·5]) were observed after L3-700 than L3-1000. The mean number of adverse events per participant did not differ between the groups (3·25 [95% CI 1·48 to 5·02] vs 3·00 [1·04 to 4·96]). Thus, L3-700 was used for vaccination in part two. In part two, ten participants were randomly assigned to receive L3-700 and five to placebo. Significantly more adverse events occurred after vaccination with attenuated larvae than with placebo (incident rate ratio [IRR] 2·13 [95% CI 2·09 to 5·51]; p=0·0030). There was no difference between groups in the frequency of adverse events after challenge (IRR 1·25 [0·78 to 2·01]; p=0·36). Most adverse events were mild in severity, with only one severe adverse event reported (erythematous and indurated pruritic rash >100 mm in a vaccine group participant after challenge). The eosinophil count increased in all participants after challenge, with a significantly greater increase among vaccinated participants than placebo participants (1·55 × 109 cells per L [IQR 0·92 to 1·81] in the vaccine group vs 0·49 × 109 cells per L [0·43 to 0·63] in the placebo group; p=0·014). Vaccinated participants had an IgG response to larval extract after challenge that was higher than that in placebo participants (increase in IgG titre 0·22 [IQR 0·10 to 0·41] vs 0·03 [-0·40 to 0·06]; p=0·020). Significantly fewer larvae per g of faeces were recovered in the vaccine group than in the placebo group after challenge (median larvae per g 0·8 [IQR 0·00 to 3·91] vs 10·2 [5·1 to 18·1]; p=0·014). The concentration of N americanus DNA in faeces was not significantly different between the vaccinated group and the placebo group (log10 DNA intensity 4·28 [95% CI 3·92 to 4·63] vs 4·88 [4·31 to 5·46]; p=0·14). Peripheral blood mononuclear cells from vaccinated participants exhibited significantly greater cytokine production at day 112 than placebo participants for IFNγ, TNFα, IL-2, IL-4, and IL-5 (p<0·05), but not IL-10.Interpretation: Vaccination with UVC-attenuated N americanus larvae is well tolerated, induces humoral and cellular responses to hookworm antigens, and reduces larval output after challenge with unattenuated larvae. Larger studies are required to confirm protective efficacy.Funding: National Health and Medical Research Council of Australia. [ABSTRACT FROM AUTHOR]

• First comprehensive proteomic analysis on S. mansoni -derived 15k and 120k vesicles. • 286 and 716 proteins were identified in 120k and 15k vesicles, respectively. • Proteins identified as antigenic targets were identified from 120k and 15k samples. • A collection of proteins with roles in host-parasite communication were identified. Helminth parasites secrete extracellular vesicles (EVs) into their environment that have potential roles in host-parasite communication, and thus represent potentially useful targets for novel control strategies. Here, we carried out a comprehensive proteomic analysis of two different populations of EVs – 15k pellet and 120k pellet EVs – from Schistosoma mansoni adult worms. We characterised the proteins present in the membranes of the EVs (including external trypsin-liberated peptides, integral membrane proteins (IMPs) and peripheral membrane proteins (PMPs)), as well as cargo proteins, using LC–MS/MS. A total of 286 and 716 proteins were identified in 15k and 120k pellets, respectively. Some of the most abundant proteins identified from both 15k and 120k pellets include known vaccine candidates such as Sm -TSP-2, saponin B domain-containing proteins, calpain glutathione-S-transferase, Sm29 and cathepsin domain-containing proteins. Other abundant proteins that have not been tested as vaccines include DM9 domain-containing protein, 13 kDa tegumental antigen and histone H4-like protein. Sm23, a member of the tetraspanin family with known vaccine efficacy, was identified in the cargo and IMP compartments of only 15k pellet vesicles. Moreover, a collection of proteins with known or potential relevance in host-parasite communication including proteases, antioxidants and EV biogenesis/trafficking of both vesicle types were identified. Our results provide the first report of a comprehensive compartmental proteomic analysis of adult S. mansoni -derived EVs. Future research should investigate recombinant forms of these proteins as vaccine and serodiagnostic antigens as well as the roles of EV proteins in host-parasite communication. [ABSTRACT FROM AUTHOR]

• Schistosoma mansoni secreted extracellular vesicles (EVs) are internalised by human endothelial and monocyte cell lines. • Internalisation of EVs induces differential gene expression in vascular endothelial cells. • Differentially expressed genes are involved in intravascular parasitism pathways including coagulation and inflammation. • Antibodies raised to S. mansoni EV tetraspanins block the uptake of vesicles by host endothelial and monocyte cell lines. The ability of the parasitic blood fluke Schistosoma mansoni and other parasitic helminths to manipulate host biology is well recognised, but the mechanisms that underpin these phenomena are not well understood. An emerging paradigm is that helminths transfer their biological cargo to host cells by secretion of extracellular vesicles (EVs). Herein, we show that two populations of S. mansoni secreted EVs – exosome-like vesicles (ELVs) and microvesicles (MVs) – are actively internalised in two distinct human cell lines that reflect the resident cell types encountered by the parasite in vivo: human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes. RNA-sequencing of HUVECs co-cultured with S. mansoni ELVs compared with untreated HUVECs revealed differential expression of genes associated with intravascular parasitism, including vascular endothelial contraction, coagulation, arachidonic acid metabolism and immune cell trafficking and signalling. Finally, we show that antibodies raised against recombinant tetraspanin (TSP) proteins from the surface of S. mansoni EVs significantly blocked EV uptake by both HUVECs and THP-1 monocytes whereas pre-immunisation antibodies did not. To our knowledge, this is the first evidence demonstrating the internalisation of secreted EVs from any helminth into vascular endothelial cells, providing novel insight into the potential mechanisms underlying host-schistosome interactions. The ability of anti-TSP antibodies to block vesicle uptake by host target cells further supports the potential of TSPs as promising antigens for an anti-fluke vaccine. It also suggests a potential mechanism whereby the current candidate human schistosomiasis vaccine, Sm -TSP-2, exerts its protective effect in animal models. [ABSTRACT FROM AUTHOR]

Herein we show for the first time that Schistosoma mansoni adult worms secrete exosome-like extracellular vesicles ranging from 50 to 130 nm in size. Extracellular vesicles were collected from the excretory/secretory products of cultured adult flukes and purified by Optiprep density gradient, resulting in highly pure extracellular vesicle preparations as confirmed by transmission electron microscopy and Nanosight tracking analysis. Extracellular vesicle proteomic analysis showed numerous known vaccine candidates, potential virulence factors and molecules implicated in feeding. These findings provide new avenues for the exploration of host–schistosome interactions and offer a potential mechanism by which some vaccine antigens exert their protective efficacy. [ABSTRACT FROM AUTHOR]